What choice does the USA have during 1940? The P-38 was problem plagued and wasn't originally designed for mass production. All you've got are the P-36, P-39 and P-40.
pretty good site for P-40 variants and history:
Index of /Variants
From the P-40 page of that site:
"In the late 1930s, the USAAC was planning to expand its force, and on
January 25, 1939. manufacturers were invited to submit proposals for pursuit aircraft. The Army was still thinking in terms of low-altitude, short-range fighters. Among the contenders were the
Lockheed XP-38, the
Bell XP-39, the
Seversky/Republic XP-41 (AP-2) and
XP-43 (AP-4), and no less than three planes from
Curtiss, the
H75R, XP-37, and
XP-42."
That is, three
in addition to the
XP-40 which had first flown
October 14, 1938 compared to (according to wikipedia:
XP-38, first flight January 27, 1939
XP-39, first flight April 6, 1938 (1939 according to America's Hundred Thousand)
"
Although the XP-40 could not match the performance (especially at altitude) of the turbosupercharged types, it was
less expensive and
could reach quantity production fully a year ahead of the other machines. In addition, the XP-40 was
based on a already-proven airframe that had been in production for some years. Consequently, on
April 26, 1939, the
Army adopted a conservative approach and ordered 524 production versions under the designation P-40 (Curtiss Model 81). At that time, it was the largest-ever production order for a US fighter, and dwarfed the service test orders placed that same day for YP-38 and YP-39 fighters. A couple of weeks later, 13 YP-43s were also ordered."
The first of roughly 200 production P-36As had begun reaching USAAC operational units in
April 1938 so it was evidently considered an aerodynamically mature design by the January, 1939 request.
The first production P-40s were apparently reaching units by
June, 1940.
Seems to me this text pretty much validates:
OK guys, The is no magic about the P-36 and P-40.
In some sense much of the
DNA of the P-36 was preserved and went on to greater glory in the form of the P-40
In a similar way, the legacy of the P-35 was evident in the successful P-47.